GUIDELINES FOR DETERMININGCAPTURE EFFICIENCY

January 9, 1995

GUIDELINES FOR DETERMINING CAPTURE EFFICIENCY

Candace SorrellSource Characterization Group A (MD-19)

Emission Monitoring and Analysis DivisionOffice of Air Quality Planning and Standards

U. S. Environmental Protection AgencyResearch Triangle Park, NC 27711

January 9, 1995

ii

TABLE OF CONTENTS

Page

1.0 INTRODUCTION . . . . . . . . . . . . . . . . . . . 11.1 Purpose . . . . . . . . . . . . . . . . . . . 11.2 Background . . . . . . . . . . . . . . . . . 11.3 Document Organization . . . . . . . . . . . . 2

2.0 RECOMMENDED CAPTURE EFFICIENCY (CE) PROTOCOLS AND TEST METHODS . . . . . . . . . . . . . . . . . . . 32.1 Permanent Total Enclosure . . . . . . . . . . 62.2 Temporary Total Enclosure . . . . . . . . . . 72.3 Building Enclosure . . . . . . . . . . . . . 9

3.0 REQUIREMENTS FOR ALTERNATIVE CE PROTOCOLS . . . . 93.1 Data Quality Objective . . . . . . . . . . . 103.2 Lower Confidence Limit Approach. . . . . . . . . 153.3 Additional Criteria . . . . . . . . . . . . . 203.4 Reporting Requirements for Alternative

CE Protocols . . . . . . . . . . . . . . . . 21 3.5 Recordkeeping Requirements for Alternative CE Protocols . . . . . . . . . . . . . . . . . . 22

4.0 MULTIPLE LINE TESTING . . . . . . . . . . . . . . . . 224.1 Aggregate Sampling. . . . . . . . . . . . . . . . 224.2 Multiple Lines/Common Control Device. . . . . . . 23

5.0 REFERENCES . . . . . . . . . . . . . . . . . . . . 24

APPENDIX

1

1.0 INTRODUCTION

1.1 Purpose

The primary purpose of this document is to provide technical

guidance to U. S. Environmental Protection Agency (EPA) Regional

Offices regarding capture efficiency (CE) testing. The document may

also prove useful to State and local agency personnel and owners and

operators of stationary sources required to determine CE.

1.2 Background

In April 1990, EPA issued new guidance on CE testing.1 This

guidance replaced the traditional liquid/gas mass balance

determinations, which had often resulted in very poor precision and

CE values well in excess of 100 percent. The new protocols involved

permanent total enclosures (PTE's), temporary total enclosures

(TTE's), and building enclosures (BE's). This guidance was later

codified as part of the Chicago Federal implementation plan (FIP) and

included in the document "Model Volatile Organic Compound Rules for

Reasonably Available Control Technology."2,3

In the beginning, the new protocols were met with resistance

from the regulated community, primarily on grounds of safety and

expense. Over time, the safety issue has largely been dispelled as

it has become clear that, with proper design and operation, PTE's and

TTE's pose minimal risk. However, it has also become clear that in

some cases, the new CE protocols are more costly than the traditional

2

liquid/gas procedures.

To address the cost issue, EPA temporarily suspended

certain federal applicability aspects of its guidance while it

embarked on a 12-month study of alternatives with potential for

reducing CE testing costs. This document is a result of that study

and of simultaneous studies voluntarily undertaken by industry

groups. In this document, EPA presents technical guidance on

recommended procedures and on alternative procedures that may reduce

costs. Revisions to current State implementation plans (SIP's) are

required to use the alternative CE test methods described herein. By

calling these procedures "alternatives", the agency does not intend

to imply that they are more difficult to approve than the

"recommended" procedures where the stated criteria for approval are

satisfied. Guidance for implementing these SIP revisions is provided

in the cover memorandum.

1.3 Document Organization

In Section 2.0, EPA's recommended protocols and test methods

are summarized. Section 3.0 presents two sets of criteria by which

alternative procedures can be approved, as well as the recommended

reporting requirements for using alternative procedures. Section 4.0

presents a technical description for aggregate sampling using the

building as a TTE and for testing multiple lines which share a common

control device.

3

2.0 RECOMMENDED CAPTURE EFFICIENCY (CE) PROTOCOLS AND TEST METHODS

The CE determination protocols and test methods recommended by

EPA are largely unchanged from those issued in the April 1990

guidance memo and codified in the Chicago FIP.1,2 The EPA continues

to recommend the use of a PTE, TTE, or BE for determining CE. When a

TTE or BE is used, either a gas/gas protocol or a liquid/gas protocol

may be selected. The EPA test methods for carrying out the

recommended protocols have been revised and will be proposed in the

Federal Register for addition to 40 CFR 51, Appendix M, as Method 204

through Method 204F. Methods 204 through 204E were originally

referred to as Procedures T, L, G.1, G.2, F.1 and F.2 respectively.

Some changes have been made to the test methods, so the latest

version of the methods, which is included as an appendix, should be

consulted when planning CE testing. The draft revisions to date are

summarized below.

First, Appendix B, section 1.4, Sampling requirements,

originally contained a requirement that the sampling time for each

TTE and BE test run should be at least 8 hours, unless otherwise

approved. This provision has been revised to specify that each TTE

or BE run shall cover at least one complete production cycle and must

be at least 3 hours long. The sampling time for each run need not

exceed 8 hours, even if the production cycle has not been completed.

4

The maximum allowable time for a test run is 24 hours. Alternative

sampling times would be subject to EPA approval.

Second, a new section on audit sample procedures has been added

to Procedure L, VOC Input.

Third, the directions for analysis audits have been

expanded (newly added for Procedure L) to include information on

audit sample availability and reporting directions for audit results.

Next, a new method, Method 204F (called the distillation

approach), has been added for measuring liquid VOC input, as an

alternative to Procedure L.

Finally, Procedures T, Criteria for and Verification of a

Permanent or Temporary Total Enclosure, and F.2, Fugitive VOC

Emissions from Building Enclosures, have been revised to clarify the

acceptability criteria of a BE and to clarify which openings

in a building constitute an exhaust point or a natural draft opening

(NDO).

Table 2-1 lists the protocols, their associated EPA recommended

CE test methods, and the formulas for calculating CE. Table 2-2

lists the EPA recommended CE test methods with the full title of

each. The PTE, TTE, and BE are discussed further in Sections 2.1

through 2.3, respectively.

5

TABLE 2-1.

EPA recommended CE test methodsa

ProtocolsEnclosure

verification

Liquid input(L)

Capturedemissions

(G)

Fugitiveemissions(F) or(FB) CE formula

PTE M204 NA NA NA Assume 100%

TTE --gas/gas

M204 NA M204B orM204C

M204D G/(G+F)

TTE --liquid/gas

M204 M204Aor

M204F

NA M204D (L-F)/L

BE --gas/gas

M204 NA M204B orM204C

M204E G/(G+FB)

BE --liquid/gas

M204 M204Aor

M204F

NA M204E (L-FB)/L

aM = EPA Method; NA = not applicable

6

TABLE 2-2.

Method 204 Criteria for and Verification of a Permanent orTemporary Total Enclosure

Method 204A Volatile Organic Compounds Content in LiquidCaptured Stream

Method 204B Volatile Organic Compounds Emissions in CapturedStream

Method 204C Volatile Organic Compounds Emissions in CapturedStream (Dilution Technique)

Method 204D Volatile Organic Compounds Emissions in FugitiveStream from Temporary Total Enclosure

Method 204E Volatile Organic Compounds Emissions in FugitiveStream from Building Enclosure

Method 204F Volatile Organic Compounds Content in Liquid InputStream (Distillation Approach)

2.1 Permanent Total Enclosure

Method 204 lists the PTE requirements and the procedures for

verifying that an enclosure qualifies as a PTE. A PTE is an

enclosure that completely surrounds a source such that all volatile

organic compound (VOC) emissions are contained and directed to a

control device. If an enclosure meets the criteria listed below then

the enclosure is a PTE and the CE for the source may be assumed to be

100 percent and need not be measured. The PTE criteria are as

follows:

1. Any NDO shall be at least 4 equivalent opening diameters

from each VOC-emitting point. An "equivalent diameter" is the

diameter of a circle that has the same area as the opening. The

7

ED '4 area

B

0.5

Eq. 1

equation for an equivalent diameter (ED) is:

For a circular NDO, this equation simply reduces to the diameter of

the opening.

2. The total area of all NDO's shall not exceed 5 percent of

the surface area of the enclosure's walls, floor, and ceiling.

3. The average face velocity (FV) of air through all NDO's

shall be at least 200 ft/min. The direction of air flow through all

NDO's shall be into the enclosure.

4. All access doors and windows whose areas are not included

as NDO's and are not included in the calculation of FV shall be

closed during routine operation of the process.4

5. All the exhaust gases from the enclosure are directed to

the control device.

If the PTE criteria are not met, then CE must be measured.

2.2 Temporary Total Enclosure

Method 204 lists the TTE requirements and the test procedures

for verifying that an enclosure qualifies as a TTE. A TTE is an

enclosure temporarily installed specifically for the CE test.4 For

an enclosure to qualify as a TTE, the criteria listed below must be

met. These five criteria ensure that all VOC's are captured for

8

ED '4 area

B

0.5Eq. 1

measurement while minimizing disruption of

the capture normally achieved by the existing capture device(s) in

the absence of a TTE.4 The TTE criteria are as follows:

1. Any NDO shall be at least 4 equivalent opening diameters

from each VOC-emitting point. An "equivalent diameter" is the

diameter of a circle that has the same area as the opening. The

equation for an equivalent diameter (ED) is:

For a circular NDO, this equation simply reduces to the diameter

of the opening.

2. The total area of all NDO's shall not exceed 5 percent of

the surface area of the enclosure's walls, floor, and ceiling.

3. The average face velocity (FV) of air through all NDO's

shall be at least 200 ft/min. The direction of air flow through all

NDO's shall be into the enclosure.

4. All access doors and windows whose areas are not included

as NDO's and are not included in the calculation of FV shall be

closed during routine operation of the process.4

5. Any exhaust point from the TTE shall be at least

4 equivalent duct or hood diameters from each NDO.

9

Two protocols may be used to measure the CE using a TTE, a

gas/gas protocol or a liquid/gas protocol. The associated test

methods and CE formula for each protocol are listed in Table 2-1.

2.3 Building Enclosure

Building enclosure protocols involve using the building that

houses the process as the enclosure. First, one must verify that the

BE meets the requirements for a TTE that are presented in Method 204.

Then, using the procedures specified in Method 204E, one must

identify all the emission points from the building enclosure (e.g.,

roof exhausts, windows, etc.) and determine which emission points

must be tested. Test procedures are given

for determining the flow rate and VOC concentration in the exhaust

from each of the various emission test points.

As with a TTE, two BE protocols may be used to measure the CE,

a gas/gas protocol or a liquid/gas protocol. The associated test

methods and CE formula for each protocol are listed in Table 2-1.

3.0 REQUIREMENTS FOR ALTERNATIVE CE PROTOCOLS

To provide flexibility, EPA has developed two sets of approval

criteria which, when either of them is met, allow the use of the data

obtained with the alternative protocols and test methods for

determining CE. Alternative CE protocols and test methods must meet

either the requirements of the data quality objective (DQO) approach

or the lower confidence limit (LCL) approach and the additional

10

criteria presented below. The DQO, LCL, and additional criteria are

described in Sections 3.1, 3.2, and 3.3, respectively. The

recommended reporting requirements for using alternative CE protocols

and test methods are discussed in Section 3.4.

NOTE: Although the Method 204 test series was developed for

TTE and BE testing, the same procedures can also be used in an

alternative CE test method. For example, a traditional liquid/gas

mass balance test could employ Method 204F to measure liquid VOC

input and Method 204 B to measure captured VOC emissions.

3.1 Data Quality Objective Approach

The purpose of the DQO is to allow sources to use alternative CE

test procedures while ensuring reasonable precision consistent with

pertinent requirements of the Clean Air Act. The DQO requires that

the width of the 2-sided 95 percent confidence interval of the mean

measured value be less than or equal to 10 percent of the mean

measured value (see Figure 1). This ensures that 95 percent of the

time, when the DQO is met, the actual CE value will be +5 percent of

the mean measured value (assuming that the test protocol is

unbiased).

11

P 'a

xavg100 Eq. 2

a 't0.975 s

nEq. 3

UCL95

"a" < 0.05 xavg

xavg 95% confidence limit

"a" < 0.05 xavg

LCL95

Figure 1. Deviation around 95 percent (2-sided) confidence interval.

Where: a = distance from the average measured CE value to the

endpoints of the 95-percent (2-sided) confidenceinterval that meets the DQO for the measured value.

LCL95 = Lower 95 percent confidence limit

UCL95 = Upper 95 percent confidence limit

xavg = Average CE value.

The DQO calculation is as follows:

where:

a = distance from the average measured CE value to the endpoints of the 95-percent (2-sided) confidenceinterval for the measured value.

12

s 'jn

i '1(xi & xavg )

2

n&1

0.5

Eq. 4

xavg '

jn

i '1xi

nEq. 5

n = number of valid test runs.

P = DQO indicator statistic, distance from the average measured CE value to the endpoints of

the 95-percent (2-sided) confidence interval, expressedas a percent of the average measured CE value.

s = sample standard deviation.

t0.975 = t-value at the 95-percent confidence level (see Table 3-1).

xavg = average measured CE value (calculated from all valid testruns).

xi = the CE value calculated from the ith test run.

The sample standard deviation and average CE value are

calculated as follows:

Individual CE values greater than 105 percent are invalid and

cannot be used to calculate the average CE and DQO. The source must

have 3 valid test runs to use the DQO approach. The DQO is achieved

when P # 5 percent. In order to meet this objective, facilities may

have to conduct more than three test runs. Examples of calculating

P, given a finite number of test runs, are shown below.

13

Number oftest runs, n t0.975 t0.90

Number oftest runs, n t0.975 t0.90

2 12.706 3.078 12 2.201 1.363

3 4.303 1.886 13 2.179 1.356

4 3.182 1.638 14 2.160 1.350

5 2.776 1.533 15 2.145 1.345

6 2.571 1.476 16 2.131 1.341

7 2.447 1.440 17 2.120 1.337

8 2.365 1.415 18 2.110 1.333

9 2.306 1.397 19 2.101 1.330

10 2.262 1.383 20 2.093 1.328

11 2.228 1.372 21 2.086 1.325TABLE 3-1. t-values.

Facility A conducted a CE test using a traditional liquid/gas mass

balance and submitted the following results:

Run CE

1 96.1

2 105.0

3 101.2

therefore:

n = 3

t0.975 = 4.30

xavg = 100.8

14

a '(4.30) (4.51)

n'11.20 Eq. 6

P '11.2110.8

100 ' 11.11 Eq. 7

a '(2.57) (6.11)

6' 6.41 Eq. 8

P '6.4196.6

100 ' 6.64 Eq.9

s = 4.51

Since the facility did not meet the DQO, they ran three more test

runs.

Run CE

4 93.2

5 96.2

6 87.6

The calculations for Runs 1-6 are as follows:

n =6

t0.975 = 2.57

xavg = 96.6

s = 6.11

The facility still did not meet the DQO. They ran three more test

runs with the following results:

15

a '(2.31) (5.33)

9' 4.10 Eq. 10

P '4.1095.7

100 ' 4.28 Eq. 11

Run CE

7 92.9

8 98.3

9 91.0

The calculations for Runs 1-9 are as follows:

n = 9

t0.975 = 2.31

xavg = 95.7

s = 5.33

Based on these results, the average CE from the nine test runs can be

used to determine compliance.

3.2 Lower Confidence Limit Approach

The purpose of the LCL approach is to provide sources, who may be

performing much better than their applicable regulatory requirement,

a screening option by which they can demonstrate compliance. The

approach uses less precise methods and avoids additional test runs

which might otherwise be needed to meet the DQO while still being

16

assured of correctly demonstrating compliance. It is designed to

reduce "false positive" or so called "Type II errors" which may

erroneously indicate compliance where more variable test methods are

employed. Because it encourages CE performance greater than that

required in exchange for reduced compliance demonstration burden, the

sources that successfully use the LCL approach could produce emission

reductions beyond allowable emissions. Thus, it could provide

additional benefits to the environment as well.

The LCL approach compares the 80 percent (2-sided) LCL for the

mean measured CE value to the applicable CE regulatory requirement.

The LCL approach requires that either the LCL be greater than or

equal to the applicable CE regulatory requirement

or that the DQO is met. A more detailed description of the LCL

approach follows:

A source conducts an initial series of at least three runs. The

source may choose to conduct additional test runs during the initial

test if it desires. All individual runs resulting in CE values above

105 percent are invalid and cannot be used in calculating the average

CE and the LCL. If the data using only the valid test runs meets the

DQO, then the average CE value is used to determine compliance. If

the data does not meet the DQO and the average CE, using all valid

test runs, is above 100 percent then the test sequence is considered

invalid. At this point the facility has the option of (a) conducting

17

LC1'xavg&t0.90s

nEq. 12

more test runs in hopes of meeting the DQO or of bringing the average

CE for all test runs below 100 percent or (b) discarding all previous

test data and retesting. [The purpose of this requirement is to

protect against test methods which may be inherently biased high.

This is important because it is theoretically impossible to have a CE

greater than 100 percent and the LCL approach only looks at the lower

end variability of the test results. This is different from the DQO

which allows average CE values up to 105 percent because the DQO sets

both upper and lower limits on test variability.] At any point

during testing when the results meet the DQO and the average CE is

less than 105 percent, the average CE can be used for demonstrating

compliance with the applicable regulatory requirement. Similarly, if

the average CE is below 100 percent then the LCL can be used for

demonstrating compliance with the applicable regulatory requirement

without regard to the DQO.

The LCL is calculated at a 80 percent (two-sided) confidence

level as follows:

where:

LC1 = LCL at a 80 percent (two-sided) confidence level.

n = number of valid test runs.

18

s = sample standard deviation.

t0.90 = t-value at the 80-percent (two-sided) confidence level (see Table 3-1).

xavg = average measured CE value (calculated from all valid test runs).

The resulting LC1 is compared to the applicable CE regulatory

requirement. If LC1 exceeds (i.e. is higher than) the applicable

regulatory requirement, then a facility is in initial compliance.

However, if the LC1 is below the CE requirement, then the facility

must conduct additional test runs. After this point the test results

will be evaluated not only looking at the LCL but also the DQO of +5

percent of the mean at a 95 percent confidence level. If the test

results with the additional test runs meet the DQO before the LCL

exceeds the applicable CE regulatory requirement, then the average CE

value will be

compared to the applicable CE regulatory requirement for

determination of compliance.

If there is no specific CE requirement in the applicable

regulation, then the applicable CE regulatory requirement is

determined based on the applicable regulation and an acceptable

destruction efficiency test. If the applicable regulation requires

daily compliance and the latest CE compliance demonstration was made

using the LCL approach, then the calculated LC1 will be the highest CE

19

LC1'94.1&(1.886)(3.55)

3'90.23 Eq. 13

value which a facility is

allowed to claim until another CE demonstration test is conducted.

This last requirement is necessary to assure both

sufficiently reliable test results in all circumstances and the

potential environmental benefits referenced above.

An example of calculating the LCL is shown below.

Facility B's applicable regulatory requirement is 85 percent CE.

Facility B conducted a CE test using a traditional liquid/gas mass

balance and submitted the following results:

Run CE

1 94.2

2 97.6

3 90.5

therefore:

n = 3

t0.90 = 1.886

xavg = 94.1

s = 3.55

Since the LC1 of 90.23 percent is above the applicable regulatory

20

requirement of 85 percent then the facility is in compliance. The

facility must continue to accept the LC1 of 90.23 percent as its CE

value until a new series of valid tests is conducted.

3.3 Additional Criteria

The Office of Air Quality Planning and Standards (OAQPS) has

developed an additional set of criteria that must be incorporated

into alternative CE protocols and associated test methods in order

for them to be approved. The following criteria apply:

1. A CE test shall consist of at least three sampling runs.

Each test run shall be at least 20 minutes long. The sampling time

for each run shall not exceed 24 hours.

2. All test runs must be separate and independent. For

example, liquid VOC input and output must be determined independently

for each run. The final liquid VOC sample from one run cannot be the

initial sample for another run. In addition,

liquid input for an entire day cannot be apportioned among test runs

based on production.

3. Composite liquid samples will not be permitted to obtain an

"average composition" for a test run. For example, separate initial

and final coating samples must be taken and analyzed for each run;

initial and final samples cannot be combined prior to analysis to

derive an "average composition" for the test run.

4. All individual test runs that result in a CE of greater than

21

105 percent are invalid and must be discarded. A test must consist

of at least 3 valid test runs.

5. If the source can demonstrate to the regulatory agency that

a run should not be considered due to an identified testing or

analysis error such as spillage of part of the sample during shipping

or an upset or improper operating conditions that is not considered

part of normal operation then the test result for that individual run

may be discarded. This limited exception allows sources to discard

as "outliers" certain individual runs without replacing them with a

valid run so long as the facility has at least 3 valid test runs to

use when calculating its DQO or LCL. This exception is limited

solely to test runs involving the types of errors identified above.

6. All valid test runs that are conducted must be included in

the average CE determination. The individual CE results and

average CE results cannot be truncated (i.e. 105 percent cannot be

reported as 100+ percent).

7. For the DQO approach the average CE for the test program

cannot be greater than 105 percent.

8. Alternative test methods for measuring VOC concentration

must include a three-point calibration of the gas analysis instrument

in the expected concentration range.

3.4 Reporting Requirements for Alternative CE Protocols

If a facility chooses to use alternative CE protocols and test

22

methods, the following information should be submitted with each

test report to the appropriate regulatory agency:

1. A copy of all alternative test methods, including any

changes to EPA reference methods, QA/QC procedures and calibration

procedures.

2. A table with information on each liquid sample, including

the sample identification, where and when the sample was taken, and

the VOC content of the sample;

3. The coating usage for each test run (for protocols in which

the liquid VOC input is to be determined);

4. The quantity of captured VOC measured for each test run;

5. The CE calculations and results for each test run;

6. The DQO or LCL calculations and results; and

7. The QA/QC results, including information on calibrations

(e.g., how often the instruments were calibrated, the calibration

results, and information on calibration gases, if applicable).

3.5 Recordkeeping Requirements for Alternative CE Protocols.

A record should be kept at the facility of all raw data recorded

during the test in a suitable form for submittal to the appropriate

regulatory authority upon request.

4.0 MULTIPLE LINE TESTING

23

4.1 Aggregate Sampling

A potential way to add further flexibility to determining CE is

to utilize aggregate sampling using a building enclosure. This

involves testing all regulated lines in the building enclosure

simultaneously. It must be noted that this technique may not be

feasible for all facilities. The applicable regulations must be

written to allow aggregate sampling and a standard must be set for

the building as a regulated entity. The building must be able to

meet the criteria in Method 204 for a building enclosure and the

building enclosure protocol described in Section 2.3 must be

followed.

4.2 Multiple Lines With Common Control Device

A second potential way to add further flexibility for

determining CE is to test multiple lines sharing a common control

device simultaneously. It must be noted that this technique may not

be feasible for all facilities. The applicable regulations must be

written to allow multiple line testing. The facility must also meet

additional guidelines as follows:

1. The multiple lines must share a common control device.

2. Multiple line testing may be performed using recommended EPA

protocols and test methods or alternative CE protocols and test

methods. The alternative protocols must meet the requirements of

Section 3.0.

24

3. The lines that are tested in combination are considered to

be in compliance only if the CE determined for the combination of

lines meets the most stringent CE required for any individual line.

5.0 REFERENCES

1. Memorandum and attachments from Seitz, J.S., EPA/SSCD, toRegional Office air division directors. April 16, 1990. Guidelines for developing a State protocol for the measurement ofcapture efficiency.

2. Office of the Federal Register. Control strategy: Ozone controlmeasures for Cook, DuPage, Kane, Lake, McHenry and Will Counties. 40 CFR 52.741. Washington, DC. U. S. Government PrintingOffice. 1992.

3. OAQPS. Model Volatile Organic Compound Rules for ReasonablyAvailable Control Technology. U. S. Environmental ProtectionAgency. Research Triangle Park, NC. June 1992. pp. 340-349.

4. The Measurement Solution: Using a Temporary Total Enclosure forCapture Efficiency Testing. EPA-450/4-91-020. August 1991. Research Triangle Park, NC.

5. Mendenhall, W. Introduction to Probability and Statistics, ThirdEdition. Belmont, California. Duxbury Press. 1971. p. 419.

25

APPENDIX

Contains Methods 204 thought 204F which can be foundon the EMTIC BBS